FreqTweak 0.6.1

FreqTweak is a tool for FFT-based realtime audio spectral manipulation and display.

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GPL (GNU General Public License) 
3.8/5 20
Jesse Chappell
ROOT \ Multimedia \ Audio
FreqTweak is a tool for FFT-based realtime audio spectral manipulation and display. It provides several algorithms for processing audio data in the frequency domain and a highly interactive GUI to manipulate the associated filters for each. It also provides high-resolution spectral displays in the form of scrolling-raster spectrograms and energy vs frequency plots displaying both pre- and post-processed spectra.

Here are some key features of "FreqTweak":

FreqTweak supports manipulating the spectral filters at several frequency resolutions (64,128,256,512,1024,2048, or 4096 bands) depending on your needs/resources.
Overlap and windowing are also selectable.
The GUI filter graph manipulators (and analysis plots) have selectable frequency scale types: 1x and 2x linear, and two log scales to help with modulating the musical frequencies.
Filters can be linked across multiple channels.
The plots are resizable and zoomable (y-axis) to allow precise editing of filter values.

The current processing filters are described below in the order audio is processed in the chain.

Spectral Analysis -- Multicolor scrolling-raster spectrogram, or energy vs. freq line or bar plots... one shows pre-processed, another shows post-processed.

EQ Cut/Boost -- Your basic multi-band frequency attenuation. But you get an unhealthy number of bands... Note that this EQ is not intended for mastering purposes, it allows for (and doesn't protect against) highly irregular filtering. Two versions, one does only frequency gain cut, the other boost.

Pitch Scaling -- This is an interesting application of Sprengler's pitch scaling algorithm (used in Steve Harris' LADSPA plugin). If you keep all the bins at the same scale, it is equivalent to Steve's plugin, but when you start applying different scales per frequency bin, things quickly get weird. For highest quality results (at the expense of transients) use larger FFT (>= 1024 bins).

Gate -- This is a double filter where a given frequency band is allowed to pass through (unaltered) if the power on that band is between two dB thresholds... otherwise its gain is clamped to 0.

Delay -- This lets you delay the audio on a per frequency-bin basis yielding some pretty wild effects (or subtle, if you are careful). A feedback filter controls the feedback of the delay per bin (be careful with this one). This is basically what Native Instrument's Spektral-Delay accomplishes. See their website for audio examples of what is possible with this cool effect.

Limit -- This is very harsh brick wall limiter on a per-bin basis. It is not very pleasant, but can be interesting.

Compressor -- This is a massively multiband compressor. It will not behave quite like a normal time-domain compressor because of the inherent block processing of the FFT. Each frequency bin has its own compressor complete with Threshold, Ratio, Attack/Release time, and makeup gain. This is *not* suitable for mastering applications!

Warp -- This one is a little different, both axes represent frequency, and the identity matrix is unaltered audio. Changing the value (height) of a bin, reallocates the energy at that frequency to the new frequency bin represented by the height of the bar. For instance, if all bins are the same height, all the frequency energy is added to a single bin. This is a sensitive filter, the Log frequency scale is helpful here (it affects both axes).

The following modulators are currently implemented, with more to come soon.

Rotate -- This will continually shift a filter horizontally at a constant definable Rate, wrapping when it reaches the edge. The edges are definable with the Min and Max Freq controls.

Rotate LFO -- The same as the above, except the shifting rate oscillates via LFO with its own Rate and Depth controls. Currently there are sine, triangle, and square waveform shapes. The frequency range that the modulator affects is definable with the Min and Max Freq controls.

Value LFO -- Shifts the values up and down with an LFO. The depth control here is percentage of total value range. The frequency range that the modulator affects is definable with the Min and Max Freq controls.

Randomize -- Randomizes the bin values between the given value bounds (as percentages of total range). Again, the frequency range that the modulator affects is definable with the Min and Max Freq controls.

What's New in This Release:

various fixes to satisfy compilers
modulator preset loading fixes

Last updated on October 29th, 2007

#spectral audio #audio processing #pitch scaling #spectral #audio #display #processing

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